1. Field of the Invention
The present invention relates to a scheduling and Radio Resource Management (RRM) technique in a cellular communication system. More particularly, the present invention relates to a method for, increasing the transmission throughput of a system by variably adjusting the boundaries among frame segments.
2. Description of the Related Art
Starting from the 1st Generation (1G) analog mobile communications including Advanced Mobile Phone Service (AMPS), wireless communication systems have evolved from 2G digital mobile communications utilizing Code Division Multiple Access (CDMA) and Time Division Multiple Access (TDMA) to 3G multimedia mobile communications known as International Mobile Telecommunications-2000 (IMT-2000) to 4G. Since 3G, the evolution has focused on provisioning of services at high rate under a wide range of environments, meeting users' demands for a variety of wireless multimedia services beyond the traditional voice communication service.
One of critical technologies behind the evolution is efficient management and distribution of frequency resources. In this context, active studies have been conducted on multi-hop transmission schemes beyond single-hop schemes, which allow only direct transmission from a Base Station (BS) to a Mobile Station (MS) in a cell. A multi-hop relay system enables both relayed transmission from a BS to an MS via an RS (Relay Station) and direct transmission from a BS to an MS.
FIGS. 1A and 1B illustrate an exemplary configuration of a conventional wireless RS multi-hop system.
FIG. 1A illustrates the configuration of a wireless RS multi-hop system with six wireless RSs. Referring to FIG. 1A, a cell 110 includes a BS 111 and six wireless RSs 112-117. An MS 118 near to the BS 111 receives a service from the BS 111, whereas an MS 119 at a cell boundary and thus having a relatively low Signal-to-Interference and Noise Ratio (CINR) receives a service from the RS 112.
FIG. 1B illustrates subcells 1-6 covered by six wireless RSs 121-126 within cell 127. The use of the RSs 121-126 effectively splits the single cell illustrated in FIG. 1A into seven cells. Because of the cell splitting, the wireless RS multi-hop system can efficiently transmit data to MSs which are located at the cell boundary or having a poor channel status or in areas having many obstacles. Consequently, the service area of the BS is expanded and shadow areas are substantially eliminated.
Compared to a conventional repeater system in which a repeaters are used to amplify the received signal, and amplify even interference from an external cell as well, a wireless RS transmits only an intended signal to an MS and can perform scheduling/RRM for MSs within the subcell covered by the RS in the wireless RS multi-hop system. In this manner, the use of wireless RSs enables data transmission to MSs in a shadow area to which the BS cannot directly transmit data and increases cell coverage and transmission throughput through additional scheduling/RRM.
While the wireless RS multi-hop system improves the reception SINRs of MSs at the cell boundary, compared to the conventional single-hop system or repeater system, it requires additional data transmission to relay data. Because transmission from a BS to an RS also occupies radio resources, part of a transmission frame should always be spared for a BS-RS link. With this limitation, as more MSs request service, each serving node (e.g. BS or RS) allocates less frequency resources at the same time and repeated transmission causes a waste of time resources. Moreover, when data is delivered to an MS over a plurality of hops, resource distribution inefficiency is increased. The resulting decrease in effective channel resources available to MSs decreases transmission throughput.
The above problems may be averted by improved scheduling/RRM, use of directional antennas, or frequency or time reuse. Nonetheless, the wireless RS multi-hop system has distinctive limitations in terms of efficient resource utilization and especially transmission throughput. Because the channel status of links involved between a BS to an MS are different, scheduling/RRM becomes very difficult and complex, if all channels on the links are considered. Also, there will be a constraint on transmission of control signals in scheduling based on information exchanged between each RS and a BS.
These limitations are caused by data transmission on a wireless link between a BS and an RS and repeated transmission of the same resources from the BS to the RS. Hence, an RoF RS technology, i.e. a wired RS system is under study, which connects a BS to an RS by an optical fiber offering excellent frequency characteristics and less data loss.